The invention relates to a method and apparatus for calibrating fabricating equipment that is used to make composite articles, laminates and similar products.
In the manufacture of tires, occasionally newly-manufactured tires have to be scrapped due to blows, i.e., small regions of trapped air within the structure of the tire that expand at the high temperatures of curing and cause bubbles in the rubber of the tire. Depending on the particular irregularity in the building process, blows can occur in the bead of the tire, the apex of the tire, the sidewall of the tire, or at the edge of the tread. Such blows may be detectable on the surface of the completed green tire, or the completed cured tire.
When a tire is cured, air that may be trapped in the rubber of the tire is vented, and it is believed that some blows occur when more than normal amounts of air are trapped in one location, and the rubber cures around the trapped air faster than the air can escape.
Pressure sensitive paper previously has been used to determine the pressure between the carcass ply and an apex on a building drum during carcass ply turn-up. Such pressure sensitive paper has a limited gray scale, and there is no way to determine the maximum pressure exerted. It is difficult to distinguish between pressure areas, and the sequence of the different pressure applications in different areas cannot be determined.
Tekscan Inc. is the manufacturer of a sensor mat that has been used by The Goodyear Tire and Rubber Company to obtain a pressure profile in tire footprints. In the conception of the present invention, the inventors speculated that such sensors can be used to obtain specific pressure profiles in tire building applications.
It is an object of the present invention to provide a method and apparatus for minimizing or preventing the trapping of air, or to at least help provide equal distribution of such air in the fabrication of a composite.
Other objects of the invention will be apparent from the following description and claims.
The invention relates to a method of calibrating pressure distribution applied at a component interface of a composite product by equipment used to fabricate the product, the method comprising the steps of (a) inserting a sensor mat adapted to detect pressure at a plurality of X, Y points between fabricating equipment and the composite; (b) taking a pressure reading and analyzing the pressure at each point of contact between the equipment and the composite; (c) adjusting the equipment to apply different pressures to the composite, if necessary; (d) repeating steps (a) and (b) to determine the pressure distribution change caused by adjusting the equipment, if necessary; and (e) repeating steps (c) and (d) until optimum pressure parameters are achieved.
The method may comprise the further step of measuring pressure distribution as a function of time.
The optimization of the method may include the further step of determining the pressure sufficient to press air from the composite, or at least distribute air in the composite so that it can be vented during curing of the composite.
In the illustrated embodiment of the method, wherein the method is used in the fabrication of a tire, step (a) comprises the further step of using a sensor mat between a turn-up bladder and tire components on a tire building machine, and step (b) comprises the further step of collecting data from the sensor in real time on a computer using a program whereby the pressure change can be viewed frame by frame in a time sequence.
More specifically, the method of fabricating a composite product comprises the steps of (a) laying up layered components of a composite; (b) calibrating fabricating equipment by (i) inserting a sensor mat adapted to detect pressure at a plurality of X, Y points between fabricating equipment and the composite; (ii) taking a pressure reading and analyzing the pressure at each point of contact between the equipment and the composite; (iii) adjusting the equipment to apply different pressures to the composite, if necessary; (iv) repeating steps (i) and (ii) to determine the pressure distribution change caused by adjusting the equipment, if necessary; (v) repeating steps ((iii) and (iv) until optimum pressure parameters are achieved, and (b) applying a pressure or pressure sequence to the layered components using the fabricating equipment wherein the pressure or pressure sequence is determined by calibration of the fabricating equipment.
Also provided is a pressure sensor mat for acquiring data on a circular or cylindrical interface, the sensor mat comprising a plurality of legs which converge into a handle portion wherein the legs contain pressure sensors, and wherein the handle is a conduit for connectors between the pressure sensors and a data recording device.
The legs may be provided with a trapezoidal shape, and sensors in the legs may have the same density in their length and width directions. The legs may have a length sufficient to use different legs to obtain measurements on both sides of a component simultaneously.